[PATCH] git-status: do not be totally useless in a read-only repository.

This makes git-status work semi-decently in a read-only
repository.  Earlier, the command simply died with "cannot lock
the index file" before giving any useful information to the
user.

Because index won't be updated in a read-only repository,
stat-dirty paths appear in the "Changed but not updated" list.

Signed-off-by: Junio C Hamano <redacted>
---

  Junio C Hamano [off-list ref] writes:

  >  [gmane=http://thread.gmane.org/gmane.comp.version-control.git]
  >
  > * "git status" is not a read-only operation.
  >
  >   It needs to do enough lstat(2) to run "update-index --refresh" to come
  >   up with the information it needs to give.  We could do so internally
  >   without writing out the result to the index (there is a patch to do
  >   this) even if a repository is not writable.
  >
  >     $gmane/39205
  >     $gmane/39206
  >
  >   However, a big downside of this approach is that doing so
  >   unconditionally would mean the expensive lstat(2) is wasted
  >   afterwards.
  >
  >     $gmane/39246
  >
  >   Currently an workaround is to run git-runstatus and live with the fact
  >   that otherwise unmodified but stat-dirty paths to show up in the
  >   output.  I think (iff somebody feels strongly about it) a possible
  >   compromise would be to see if we can update the index, and do what the
  >   current code does if we can, and otherwise fall back on the new code
  >   that does the internal "update-index --refresh".

  I did not feel strongly enough about it, so here is another
  approach.

 git-commit.sh |   21 +++++++++++----------
 1 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/git-commit.sh b/git-commit.sh
index ec506d9..cfa1511 100755
--- a/git-commit.sh
+++ b/git-commit.sh

@@ -13,10 +13,10 @@ git-rev-parse --verify HEAD >/dev/null 2>&1 || initial_commit=t
 case "$0" in
 *status)
 	status_only=t
-	unmerged_ok_if_status=--unmerged ;;
+	;;
 *commit)
 	status_only=
-	unmerged_ok_if_status= ;;
+	;;
 esac
 
 refuse_partial () {

@@ -389,16 +389,17 @@ else
 	USE_INDEX="$THIS_INDEX"
 fi
 
-GIT_INDEX_FILE="$USE_INDEX" \
-	git-update-index -q $unmerged_ok_if_status --refresh || exit
-
-################################################################
-# If the request is status, just show it and exit.
-
-case "$0" in
-*status)
+case "$status_only" in
+t)
+	# This will silently fail in a read-only repository, which is
+	# what we want.
+	GIT_INDEX_FILE="$USE_INDEX" git-update-index -q --unmerged --refresh
 	run_status
 	exit $?
+	;;
+'')
+	GIT_INDEX_FILE="$USE_INDEX" git-update-index -q --refresh || exit
+	;;
 esac
 
 ################################################################

-- 
1.5.0.1.619.g04c5c